Safe, Portable Power Source

In an operating theatre, much of the equipment exists to protect the health of the patient. Equally important, however, is protection of the health of the medical staff, but this barrier must not impair their vision or freedom of movement.

A surgical protection suit is the doctor’s first and most important line of defense. An important element of the suit is the helmet, as this provides clean, uncontaminated air for the surgeon to breathe, and a protective visor that offers a clear and unobstructed view of the patient without misting.

Today’s most advanced surgical helmets include a powerful LED light to illuminate the area of the patient’s body that the surgeon is focused on, and a multi-speed fan to ventilate both the helmet and the body of the suit. Since the surgeon requires complete freedom of movement, the suit cannot be tethered to a main power supply. A high-tech surgical protective suit will therefore include a battery power unit. The latest helmet includes a custom lithium-ion battery pack from Varta Microbattery that balances the constraints of size, weight, run-time, and reliability.

An important element of the suit is the helmet, as this provides clean, uncontaminated air for the surgeon in the operating theatre to breathe. A protective visor offers a clear and unobstructed view of the patient without misting. (Source: Varta)

Challenging combination of design requirements
The portable power supply in a surgical helmet must balance a number of apparently opposing requirements.

A complex medical operation can last for several hours. If the power in the helmet failed -- which would cause the LED light to dim and the visor to become misted as the fan stopped working -- the resulting interruption to the surgeon’s activity could cause serious harm to the patient. The battery pack must therefore offer high energy capacity to sustain continuous operation over many hours, and predictable power delivery. The theatre crew must be able to read out the State of Charge (SoC) of the battery, and to estimate accurately the remaining run-time on the basis of the SoC value.

In general, the bigger the battery, the greater its energy capacity and the longer its run-time between charges. But at the same time, the helmet must be light and comfortable, since the surgeon will wear it for long periods. The battery pack must therefore be as small and light as possible. It must also be capable of tolerating the difficult conditions inside a protective suit: high humidity caused by vapor in the wearer’s exhaled breath, as well as potential exposure to contaminants and high temperatures.

Finally, compliance with FDA regulations governing end products requires that suppliers of key components such as power supplies verify or validate that their products perform as specified, to within precisely defined tolerances.

Several studies indicate that the noise generated by performing orthopaedic surgery has the potential to cause hearing loss. Noise produced by several orthopaedic surgical instruments such as saws, drills, and hammers during surgery exceeds 100 dB, especially during knee replacement procedures. Surgical protection suit may help to protect surgeon from noise-induced hearing loss.

I like the idea of a display, Greg - that would allow the user to know immediately whether or not the battery should be considered for service without any additional steps. Sounds like a good PIC project to me ;)

Yes, the data chip idea would be nice. Ideally, the charging station would have some type of display which would show the user what percent of charging cycles are left in the battery (and warn if a battery should be replaced soon).

That's a great idea, Greg - from a reliability standpoint they could then discard the battery before it neared the end number of its specified charge cycles - in a critical application such as this that might be a good approach to ensure sufficient battery life. For example - maybe a battery that is spec'ed at 500 charge cycles you could pull it out of service at 400 charge cycles.

It would be really nice to have a data chip in the battery pack that keeps track of the number of cycles and the maximum temperature of the battery pack - that might help you be able to tell when a failure is imminent.

Good point about monitoring remaining run-time to avoid unexpected power-down during operation. Is there also a feature on the charging station which monitors the number of charges each individual battery pack receives? (monitoring charge cycle life).

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